The present invention relates to orthopedic surgical devices, particularly intramedullary nails for surgical placement in a patient""s long bone, such as a femur. More particularly, the present invention relates to an improved intramedullary nail assembly that enables the implant to be used in the treatment of children above 2 years of age and below 65 kilograms of body weight.
Intramedullary nails have long been used for internal fracture fixation, and have become the preferred implant treatment in many long bone fracture cases. Generally, such a device comprises an extended hollow shaft having a predetermined cross-section and provided with transverse apertures at selected locations along its length. The nail is inserted into an intramedullary canal of a long bone and secured within the bone by transverse bone screws placed through aligned apertures in the nail. The general configuration of intramedullary nails is well illustrated in U.S. Pat. No. 5,935,127, issued to Border on Aug. 10, 1999.
Because the length of the intramedullary nail must be matched to the length of the bone to be repaired, prior art intramedullary nails are produced in a variety of lengths and diameters. In order to limit the number of sizes which must be carried in inventory, recent intramedullary nails have been produced as modular systems having a limited number of base nail members provided in a uniform length and a much larger variety of extension members in varying lengths and diameters. A selected extension member can be joined to any selected base nail member to produce an intramedullary nail of any desired length. One type of modular intramedullary nail system has been disclosed by Engelhardt et al in U.S. Pat. No. 4,805,607. The intramedullary nail of Engelhardt is provided with an extension member available in different lengths and diameters. Another improved type of modular intramedullary nail system has been disclosed in U.S. Pat. No. 5,122,141, issued to Simpson et al on Jun. 16, 1992, which provides a modular intramedullary nail system capable of rotatably receiving a variety of extension members of a selected length, the extension members capable of being secured in any desired angular orientation relative to the base portion of the intramedullary nail.
The modular intramedullary nail systems described in the above two United States patents are advantageous in providing a femoral intramedullary system capable of being adapted to a variety of different length bones, and eliminating a requirement for a precise rotational positioning of the nail prior to insertion of the nail into the intramedullary canal for receiving the transverse bone screws. Nevertheless, the intramedullary nail system is not self-adjustable in length and, therefore, is incapable of providing a surgical fixation to stabilize fractured bones during the healing process without disrupting the normal bone growth particularly of a child patient.
In another example described in U.S. Pat. No. 5,057,103, issued to Davis on Oct. 15, 1991, an adjustable feature is incorporated into a nail that is inserted into the medullary canal of a fractured bone to fixate the bone segments in order to promote healing. The nail provides compressive force to close the fracture and further promote healing. The nail has an outer member and an inner member that is slidable within the outer member. The inner member, at one end, has arms for engaging the interior of the bone cortex in the distal bone segment and, at the other end, a holding member for engaging the cortex in the proximal bone segment. The arms are movable between stowed positions, for allowing insertion of the nail into the bone, and deployed positions for engaging the bone cortex. The force exerted by the arms and the holding member on the bone is adjustable. The adjustable feature essentially provides a mechanism for adjusting the compressive force applied to the bone and does not permit the length of the nail to be adjusted particularly after its implantation.
Prior art located through a diligent search has failed to show references to adjusting solutions for this regard. Therefore, there is a need for an extendable intramedullary nail system for surgical fixation of fracture bones of child patients.
It is one object of the present invention to provide an intramedullary nail assembly self-extendable in length for surgical fixation of fractured bones of child patients.
It is another object of the present invention to provide an intramedullary nail system for surgical fixation of fractured bones without transverse bone screws.
It is a further object of the present invention to provide an intramedullary nail assembly which can be implanted in a relatively easy method.
Generally, an intramedullary nail assembly for use in fixation of long bone fractures, in accordance with one aspect of the invention, comprises a telescopic rod having two opposed ends and including a female component and a male component telescopically interconnected to permit axial movement of the ends relative to each other; and means for anchoring each end of the telescopic rod to either end of a fractured long bone when the telescopic rod is implanted in the long bone and extends longitudinally through a length of the bone so that the length of the telescoping rod is extendable as the bone heals and normal patient growth occurs.
More especially, according to an embodiment of the present invention, the intramedullary nail assembly is provided with an elongated tube having one end thereof formed with an external thread that preferably has a diameter greater than the external diameter of the tube, and a rod having one end thereof formed with an external thread that is preferably a self-tapping screw with a diameter as large as the external diameter of the tube. The rod is slidably and detachably received in the elongated tube to form the telescoping nail assembly with the threads at opposed ends thereof. The rod is adapted to be separately inserted through the intramedullary canal into the bone until the self-tapping screw is anchored in either end, preferably the distal end of the bone, and the rod spans the fracture. The elongated tube is adapted to be inserted through the canal into the bone to receive the rearward end of the rod sliding into the tube until the external screw at the rearward end of the tube is anchored in the end, preferably the proximal end of the bone. The intramedullary nail assembly, according to the present invention, inhibits radial displacements of the fractured segments of the bone while the nail assembly is axially extendable as bone structures heal and normal patient growth occurs.
The intramedullary nail assembly, according to the present invention, has a unique feature of self-adjustment in length after its implantation to provide a fixation of the fractured bone segments to promote healing without disrupting normal patient growth, which is particularly advantageous when the nail assembly is used for children above two years of age and below 65 kilograms of body weight. Additionally, the nail assembly, according to the present invention, provides a relatively easy method of implantation because there are no transverse bone screws required. The anchorage of the nail assembly is achieved through rotating the respective rod and tube components to let the threads thereon anchor in the bone structures. The rotation of the respective rod end tube is achieved through driving tools detachably connected thereto.